A conventional liquid surface detection device is, for example, disclosed in PTL 1. In this liquid surface detection device, as a magnet rotates with a shaft along with vertical motions of a float that follows fluctuations of the liquid surface, output voltage of a magnetic resistance element, more specifically a magnetic detection element, which is attached to a body opposite the magnet, changes. A position of the float, in other words, a liquid surface of the fuel, is detected by the output voltage of the magnetic resistance element. The liquid surface detection device can be made smaller by reducing a projected area viewed from the rotary axis direction of the magnet by placing the magnetic detection element on the rotary axis of the magnet or in the rotary axis direction of the magnet.